NDUFS3 and Leigh syndrome: Compound heterozygosity for Ndufs3 mutations (T145I and R199W) has been reported in 1 patient with late-onset Leigh syndrome, optic atrophy, and CI deficiency (21), whereas the compound heterozygosity for the mutations (R140W and R199W) has been associated with early-onset Leigh syndrome and severe reduction in CI levels (23, 24).